Amateur Radio in the International Space Station, or ARISS and the Space Shuttle Amateur Radio Experiment, or SAREX, provide HAM radio operators as well as students with the unique opportunity to talk by radio with astronauts in the ISS orbiting the Earth traveling about 27,360 kilometers (17,000 miles) per hour. With the help of amateur radio operators on the ground, students attempt to contact the astronauts by voice, packet-radio or slow scan television depending on the equipment operational at that moment on the ISS.
The initial HAM station phase 1 is located in the Russian Zarya (functional cargo) module, see the above picture of Jeff Williams, KD5TVQ. And HAM station phase 2 is located in the Zvezda (service/living quarters) module, see the picture below of Mike Fincke holding the Kenwood TM-D700 and Yuri Lonchakov holding the microphone. The Earth facing WA-1 and WA-2 antennas, that are placed on the handrail of the Zvezda service module, are used for the crossband repeater and APRS digipeater/BBS. The latest addition to the HAM radio equipment is the installation of ARISS antennas on the European Space Lab Columbus. Have a look at this animation of the steps in the assembly of the International Space Station.

If you want to see if the International Space Station is in range of your location, or want to see whether the repeater, the APRS digipeater/packet radio BBS, or the SSTV camera is active, you can visit the ISS Fanclub Homepage. Or you can check at KD5QGR's Live Oscar Satellite Status Page to see the operational status of the ISS. The International Space Station is either active with a voice repeater (uplink 437.800 Mhz FM / downlink 145.800 Mhz FM), with APRS (uplink and downlink 145.825 Mhz FM) or with Slow Scan TeleVision (downlink 145.800 Mhz FM). Beside scheduled schoolcontacts, crew contacts only occur when the tight time schedule of the crew allows this, i.e. during "sleep". Daily reports of the crew of the ISS (experiments, sleep/wake shift planning, science update, etc.) can be viewed at NASA's Office of Space Operations. I copied several student contacts with the ISS commander Mike Fincke (KE5AIT), and captured a school contact and several SSTV images when "space tourists" Richard Garriot (W5KWQ) and Charles Simonyi (KE7KDP) were operational. The last round of SSTV images came from the Russian MAI-75 experiment (Moscow Aviation Institute) RS0ISS. See the ISS fanclub or the ariss-sstv blogspot for the latest information on SSTV transmissions from the ISS.